Technical Articles Relating To Off-Road Vehicle Development

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MillerMatic 251 Product Review

Published by Trails Less Traveled on March 7th, 2006


Shopping for a 220-Volt MIG-Welder

Shopping for a welder is a lot like shopping for anything else; you look for features/performance, quality/durability, price, etc. But there are a few more specific things to consider that will help you find the right machine. Start by considering what type of material you’ll be working with most often. With MIG welders, bigger is usually better, but you don’t need to over-spend. Be realistic about your need and balance that against your budget. Duty Cycle is another term that’s important to understand. This the amount of time during a ten-minute period that a power source can run at it’s rated output without overheating. Visit Miller’s website if you have any questions about welding terms.

After assessing our needs, I did some research online and posted this question on the Miller Motorsports forum. I was able to narrow my search down to four welders that I was seriously considering. Miller and Lincoln are the two most respected names in welding and I knew I couldn’t go wrong either way, but I like to make informed decisions. There was the MillerMatic 210, the Lincoln 215, the MillerMatic 251 and the Lincoln 255. Everything I turned up told me that these are all great welder and in the end, I decided to purchase a Miller welder, mostly because of the number of people in the industry that use this machine and swear by it. My local welding supply store also carries Miller welders and stocks a variety of consumable and replacement parts. Another selling point is Miller’s customer service. Their Signature Service that is a commitment to provide customers with free 2-day air on all consumable/replacement parts! That kind of support really means a lot to people that make a living using these tools and it means I’ll never be stranded in the middle of a project, waiting for parts. I went ahead and splurged on the MillerMatic 251 because it was only $500 more expensive than the MillerMatic 210 and it was be easy to justify that over the life of the equipment. The value added is in the higher voltage output rating (200 Amps at 28 V, 60% duty cycle vs. 160 Amps at 24.5 V, 60% duty cycle) and wider Amperage range (25-700 IPM vs. 35-700 IPM). I also really liked the digital readout on the control panel.


I’ve included links to some of the videos on Miller’s website that explain how to set up a new Miller welder. This is an Overview of the steps involved.

Millermatic 251= Inside Panel=

So what’s in the box? There’s a lot going on in there, but let’s start with the power source. Miller’s introduction to electricity in welding interactive tutorial includes a good explanation of the differences between single phase and three phase power sources, and their electrical set-up video describes how to set-up the jumper links to accommodate different input voltages.

changing spools= spool comparison=
Loading wire spools is also quick and easy thanks to Millers’ simple tool-free design. The MM251 can accommodate a massive 44lb spool of wire, which is much more cost effective than purchasing smaller spools (like the empty 12lb spool shown next to our new spool of .035 wire). .035” (9mm) wire works great for most of the projects around our shop.

open drive roll=
The wire feeding mechanism pulls wire from the reel and feeds it to the MIG gun. The MM251 features dual drive rolls for consistent wire feeding and uses durable steel and cast aluminum metal parts. The drive rolls can be changed quickly to accommodate different wire sizes and the drive roll tension is also easy to adjust. No tools are required.

closed drive roll=
The polarity should come pre-set to Electrode Positive (DCEP), and is suitable for most types of MIG welding, including solid steel, stainless steel, aluminum, or flux core with gas wires (GMAW). Reversing the polarity to Electrode Negative (DCEN) is only necessary when welding with gasless flux core wires (FCAW).

MIG gun= control panel plug-in=
Installing the MIG gun (see previous video) is only a matter of feeding the lead through the control panel and tightening it into the wire feeding mechanism. The MillerMatic 251 comes with a 12ft, 250 Amp M-225 MIG gun, which is a good match for this welder. I haven’t had any problems getting it into tight/awkward spaces, especially when using some of the the smaller orifice nozzles and tapered contact tips. I’ve been frustrated with the 12ft gun while working in a small shop though, where it would be nice to have a little longer reach so I didn’t have to drag the welder around the garage behind me. On a related note; take care of your MIG gun and feeder cable. This should make sense when you stop and think about it, because wire isn’t easy to feed through a tangled and kinked liner. Weld quality will suffer any time the wire feed speed is inconsistent.

ground clamp=
The work clamp/ground is connected to the negative terminal next to the drive roll mechanism at one end and to the work-piece at the other end. The ground completes the electrical circuit while welding, so an effective ground is essential. Make sure that you’re clamped to clean, bare metal and try to keep the ground relatively close the area being welded.

control panel=
The MillerMatic 251’s control panel is very user-friendly, with an easy-to-read digital readout and two dials to control the settings. So, what do those dial mean and how do you adjust them?

Well, the top dial sets the weld power output voltage, which is best described as the pressure or force that pushes electrons through a conductor. Voltage does not flow, but causes amperage or current to flow. Voltage is sometimes termed electromotive force (EMF) or difference in potential.

The bottom dial controls wire feed speed (measured in inches per minute) and Amperage. Amperage is determined by wire feed speed and is a measurement of the amount of electricity flowing past a given point in a conductor per second (current is another name for amperage).

reference chart=
Do you need to understand all of that in order to use a MIG welder? Not really. Every Miller includes a reference chart that helps users find the right settings for different types and thicknesses of material, as well as different wire types and shielding gases. An interactive version of their MIG welding calculator can also be found on Miller’s website. Keep in mind that while the recommended settings will get you in the ballpark, spending some time learning the subtleties of your machine and fine-tuning those adjustments to suit different applications and welding techniques will yield the best results.

accessory tray=
There is a removable accessory tray inside the welder right above the drive roll mechanism. It’s a handy place to keep an assortment of contact tips and spare nozzles, etc. You can purchase a set of dedicated welding pliers, but I’ve found that a regular old pair of needle-nose pliers with a wire cutter work just as well.

digital readout from a distance=
The digital readout on the control panel is an especially nice feature because the settings are easily readable from a distance. The display shows the actual output voltage while welding (and for 5 seconds afterwards), so the operator can verify consistent power supply/delivery.

Another nice feature is the ability to adjust the run-in wire-feed speed. That’s the wire speed for the first few seconds after starting a new weld. It’s nice to be able to dial that down and get a good amount of heat into the beginning of a weld, as opposed to starting cold and finishing hot. The factory setting is 100%, but this is easily adjusted by turning the welder on while holding the trigger down. The numbers on the lower dial will flash 888 and then display the current setting. Adjust the dial and then turn the machine off and back on.

shielding gas tank=
Shielding gas is stored in a gas cylinder under pressure. Most commonly, it’s a mixture of 75% Argon and 25% Co2. Tanks can either be rented or purchased outright, but they’re all refilled on an exchange basis. They’re all manufactured to the same standards, so there’s not really any difference between brands, although some places do take much better care of their tanks than others.

If you’re not going to be refilling the tank frequently, purchasing a tank outright might be the best option. Welding supply shops aren’t making any money if their rented tanks aren’t being refilled, so many of them charge higher rates for long-term rentals. I ended up buying a 250 cubic foot tank because I’ve never needed to refill a larger tank more than once every couple of months. Regarding size, it’s much more cost-effective to fill a larger tank and they all have a similar footprint, so saving space isn’t really a factor when you’re talking about a 220V MIG welder. IMPORTANT: If you buy a tank, make sure that the ring around the neck says ‘Customer Owned’ and keep your original receipt as proof of purchase.

pressure regulator=
The cylinder valve on the far right is part of the tank and the two gauges on the left are included with the MillerMatic 251. When the cylinder valve is opened, the gauge on the right displays pressure in the tank and the gauge on the left displays the regulated pressure. Adjusting the regulated pressure is as simple as turning the T-handle on the front of the regulator. The included gauges work just fine, but I prefer to use a regulator with a floating ball that indicates regulated pressure because it’s easier to see from a distance.

shielding gas connection=
The shielding gas is delivered through this hose to, into the welder and then travels through the MIG gun, to be dispensed at the weld area. Also note the power supply cable coming out of the machine right below the gas connection.

220V male connection= 220V female connection=
This is the other end of the 220-Volt electrical supply cord. If your garage isn’t already wired for 220, that would obviously need to be addressed. The picture on the right shows what type of 220 outlets should be installed. Heavy-duty 220V extension cords are pretty expensive. It’s much cheaper to build your own by purchasing all of the parts from a hardware store. If you’ve never done this before, ask for assistance when you buy the parts. There are only three wires to connect at each end, so it’s really easy.

gun holster open= gun holster closed=
The newer MM251’s include two gun holsters that are integrated into the side of the welder. The cradle folds out of the way when it’s not being used, although I only folded mine up for the first time since unpacking it to take these pictures. It’s a really convenient way to store your welding gun and ground clamp.

Why two gun holsters? Because the MM251 is set up to accommodate a spool gun for welding aluminum. Miller calls it their gun-on-demand system, which means that both guns can be plugged-in at once and power automatically switches to the gun you need whenever you pull the trigger on either one (they cannot both be used at the same time). I chose not to buy the spool gun because we don’t need to weld aluminum very often and the welder itself is already a big-budget item. You can always buy one later.


coiled gun and ground clamp= covered MIG welder=
I like to coil the gun and ground clamp and keep the welder clean under this Miller cover. It fits the machine very well and it’s a great way to protect your investment if your welder is stored in the same area where grinding dust or debris is in the air. This is a real problem in smaller shops where you might not have the luxury of designating different spaces for different types of work.

big window elite outside= big window elite inside=
Miller’s Big Window Elite is the nicest welding helmet that I’ve had the opportunity to use. The extra-large auto-darkening panel lets me see everything around the work area and the adjustable lense gives me different levels of sensitivity for different environments. It’s lightweight and the headband is super-comfortable. The battery-powered helmet is also solar-assisted, so when you’re welding, you’re also regenerating the charge in the helmet. I thought that was a pretty slick detail. Don’t worry about those burn marks and scratches; clear protective lenses protect the actual welding lens on the inside and outside.

welding cap=
Burning hair smells bad and picking molten bits of metal out of your scalp is NOT fun. It seems like most of our welding projects involve contorting myself into uncomfortable positions in awkward places. I first started wearing welding caps like these when I was doing overhead welding and now I wear them in the shop almost all the time. I haven’t found a real need to wear heavy leather welding jackets, but I try to avoid wearing synthetic (flammable) materials around sparks and flames.

welding gloves=
There are many different type of welding gloves. I’d suggest buying several pairs at once and leaving them around the shop. It’s helpful to have a pair of gloves handy almost any time you need to handle steel. The lightweight yellow gloves on the right really shouldn’t have been used for welding at all and you can see how they burned right through on the backs of the knuckles. I found the brown pair of welding gloves in the $5 bin at the local hardware store- see how heat has shrunken and deformed the cheap leather on some of the fingers. The newer pair of white welding gloves in the top of the picture was purchased at a welding store for less than $10 and they’ve held up very well. I like to buy gloves that are light enough that I can still handle angle grinders and other tools that I use frequently while welding.

Getting Started

welding table=
A sturdy welding table is something that your knees and back will really appreciate. Having a flat level surface to weld on also makes fitting parts together much easier. Necessity and space will dictate what type of table will work best for you, but there are several things to keep in mind. Make sure to build the tabletop out of something nice and flat, and it should be heavy enough that it won’t warp. It’s nice to have a tabletop that extends several inches over the framework so you can clamp things down to it. You can outfit your welding table with anything else that suits you. Power outlets, wheels, tool boxes, etc.

material prep=
Material prep is the first step to making good welds. Don’t be in too big of a hurry to clean off the paint, rust, or anything else that might contaminate your welds. Fitment is the next big challenge. Tube notching and prepping material is a topic that we’ll cover in a lot more detail in future articles.

Order of assembly is an important consideration anytime you’re welding parts together, because once two pieces are joined, you can’t easily separate them to complete welds that are difficult to get to. At this junction, you can see that we had to completely weld the underside of the top tube before fitting the bottom tube in order to make sure that every tube got welded around 360-degrees.

We’re not going to talk much further about MIG welding techniques in this article. Instead, we’ll publish another installment with interviews and tips from real welding experts, but I thought some of you might like to see how we’ve put our new Miller welder to work.

rollcage= engine-cage=
This is a continuation of the utility bedcage that we built for the Trails Less Traveled Tacoma project truck. It’s also a great example of the type of work that requires a welder to get into tight and awkward spaces. I’ve got to stress that before building a rollcage, you should first be confident that you can design a safe rollcage. This is the most critical type of fabrication work and the consequences can be disastrous if it fails when you need it. I don’t mean to be dramatic, but it’s a serious subject.

rusted plate= prepped and tack-welded plate=
I’ve found that material prep affects my weld quality just as much as technique, so make sure to take your time stripping those old framerails. Using a combination of clamps and tack-welds to keep parts from warping. Also move around and give the material time to cool in between welding if it’s an especially heat-sensitive part.

cutting wheelwells= tack-welded wheelwells=
Sheetmetal work is a breeze with the MillerMatic 251. I dialed the settings down and was able to these 4Runner wheel-well openings back together after enlarging them to fit 35” tires. I’ve been really impressed with the versatility of this welder and I’ve been using the 44lb spool of .035” wire for EVERYTHING. Switching to .023 or .030” wire would probably allow us to weld thinner sheetmetal without warping or burning through, but I don’t do much bodywork.

welding an exhaust system= exhaust detail=
If you want a job done right…
It has always irritated me when I check the work that I’ve paid an exhaust shop to do for one of my vehicles only to see that I could have it better myself. I recently ordered an assortment of mandrel bends in different sizes that we have used to build several exhaust systems.

Jeep CJ7 grill shell 1= Jeep CJ7 grill shell 2=
We’ve done a little bit of everything with this welder. I built a custom radiator mount into this grill-shell for our CJ7 and used a series of evenly spaced tack-welds to avoid warping the thing grill shell.

powertank straight jacket Co2 bottle mount=
I hate bolting brackets onto brackets. We took this Straight Jacket Powertank mount, which was designed to be a bolt-on part, and welded it right into the rollcage on our Tacoma for a super-clean (and permanent) installation.

This Article was originally published on April 2006


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